In New Delhi’s Qutb Minar, visitors can find a 7.2-meter high iron pillar weighing 6 tons in the courtyard of the Quwwat-ul-Islam mosque, which remains intact despite being exposed to sun and rain for 1,600 years. Scientists began studying the iron pillar in 1912 and discovered in 2003 that it was made of wrought iron containing high phosphorus levels and no sulfur or magnesium, contributing to its durability. The pillar also has a thin layer of misawite on its surface, formed through catalysis with high levels of phosphorus in iron.
The ancient craftsmen used a technique called forge welding, heating and hammering the iron to keep the high phosphorus levels intact. This non-traditional method, along with the compound of iron, oxygen, and hydrogen found on the surface of the pillar, enhances its durability. The iron pillar, believed to have been built during the Gupta empire, serves as a symbol of India’s ability to forge iron in ancient times and is surrounded by a moat built by the Archaeological Survey of India.
Despite the environmental conditions and pollution in the Indian capital, the iron pillar remains standing as a testament to ancient metallurgy. Today, the pillar is a symbol of scientific institutions in India and continues to be a subject of study and admiration for its durability and craftsmanship.